Method of limiting a load applied on a seat belt in an emergency

ABSTRACT

A method of limiting a load applied on a seat belt in an emergency, includes obtaining information, judging if the emergency situation is in a first situation wherein a predetermined condition for controlling one seat belt load limiting mechanism is not satisfied based on the information, or in a second situation wherein the predetermined condition is satisfied; and in the first situation, the method further performs actuating a driving member not to operate the one seat belt load limiting mechanism, winding the seat belt to remove a slack of the seat belt with actuating the driving member, and operating another seat belt load limiting mechanism to prevent withdrawing the seat belt; and in the second situation, the method further performs winding the seat belt without actuating the driving member, and operating the one and another seat belt load limiting mechanisms to prevent withdrawing the seat belt.

CROSS-REFERENCE TO RELATED APPLICATION

This is a continuation application of Ser. No. 12/585,599 filed on Sep.18, 2009, which claims priorities of Japanese Patent Application No.2008-293396 filed on Nov. 17, 2008, and Japanese Patent Application No.2009-027179 filed on Feb. 9, 2009.

BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT

The present invention relates to a technical field of a seat beltretractor for winding up a seat belt while allowing winding andwithdrawal of the seat belt. More particularly, the present inventionrelates to a technical field of a seat belt retractor provided with aseat belt load limiting mechanism (hereinafter, sometimes referred to as“EA mechanism”), which, by means of an energy absorbing member such astorsional deformation of a torsion bar, limits load acting on the seatbelt to absorb energy added to an occupant when the seat belt is lockedin the event of an emergency such as a vehicle collision where a largedeceleration acts on the vehicle under the condition that the occupantwears the seat belt, and a seat belt apparatus having the same.

Conventionally, a seat belt apparatus installed in a vehicle such as anautomobile restrains an occupant with a seat belt thereof in the eventof the emergency as mentioned above. The seat belt apparatus comprises aseat belt retractor. In the seat belt retractor, the seat belt is woundonto a spool when the seat belt apparatus is not used and is withdrawnfrom the spool to be worn by the occupant when the seat belt apparatusis used. A locking mechanism of the seat belt retractor is actuated inthe event of an emergency as mentioned above so as to prevent the spoolfrom rotating in a belt withdrawing direction, thereby preventing theseat belt from being withdrawn. Accordingly, the seat belt restrains theoccupant in the event of the emergency.

In the seat belt retractor of the conventional seat belt apparatus, theoccupant is forced to move forward due to large inertia because a largedeceleration acts on the vehicle when the seat belt restrains theoccupant in the event of the emergency such as the vehicle collision.Accordingly, a large load is applied to the seat belt and the occupantreceives a significant force from the seat belt. This force does notcause a serious problem to the occupant, but it is preferable to limitthis force.

For limiting this force, a seat belt retractor has been proposed whichis provided, in addition to a torsion bar, with a second EA mechanismwhich can operate independently so as to further flexibly and variouslyset the limited load applied on the seat belt according to informationin the event of the emergency (for example, see Japanese UnexaminedPatent Application Publication No. JP-A-2008-114659: Patent Document 1).According to the seat belt retractor disclosed in Patent Document 1, thelimited load can be flexibly and variously set according to thesituation in the event of the emergency. Therefore, it is possible toeffectively and suitably restrain the occupant during the vehiclecollision.

In the seat belt retractor disclosed in Patent Document 1, it isnecessary to activate a gas generator for the second EA mechanismwhenever the second EA mechanism is operated. Therefore, the second EAmechanism cannot be effectively operated.

The present invention has been made under the aforementionedcircumstances and an object of the present invention is to provide aseat belt retractor wherein, in addition to a first EA mechanism, asecond EA mechanism is independently and effectively operated so as toflexibly and variously set the limited load applied to the seat beltdepending on the emergency situation, and a seat belt apparatus havingthe same.

Further objects and advantages of the invention will be apparent fromthe following description of the invention.

SUMMARY OF THE INVENTION

To solve the aforementioned problems, a seat belt retractor according tothe invention comprises: a spool onto which a seatbelt is wound; a firstseat belt load limiting mechanism for limiting load applied on said seatbelt when an emergency occurs; a second seat belt load limitingmechanism for limiting load applied to said seat belt when the emergencyoccurs and a predetermined condition based on the emergency situation issatisfied; a driving member for actuating said second seat belt loadlimiting mechanism; and a controller for controlling said drivingmember, wherein the controller actuates said second seat belt loadlimiting mechanism by not actuating said driving member when saidpredetermined condition is satisfied, and does not actuate said secondseat belt load limiting mechanism by actuating said driving member whensaid predetermined condition is not satisfied.

According to the present invention, when said controller determines thatthe actuation of said second seat belt load limiting mechanism isrequired, but the entire operation of said second seat belt loadlimiting mechanism is not required, said controller stops the operationof said second seat belt load limiting mechanism by actuating saiddriving member after said second seat belt load limiting mechanism isactuated and before the entire operation of said second seat belt loadlimiting mechanism is completed.

A seat belt retractor according to the present invention furthercomprises a locking mechanism having a locking member which isconfigured to normally rotate together with said spool by transmissionof rotation of said spool via the first seat belt load limitingmechanism and is prevented from rotating in the seatbelt withdrawingdirection when the emergency occurs, wherein when said locking member isprevented from rotating in the seat belt withdrawing direction so thatsaid spool rotates in the seat belt withdrawing direction relative tosaid locking member, load applied on said seat belt is limited by atleast said first seat belt load limiting mechanism.

Further, said second seat belt load limiting mechanism comprises asupporting member for the energy absorbing member which is disposedcoaxially with said spool and rotatable relative to said spool, and anenergy absorbing member which is disposed between said locking memberand said supporting member and is deformed by rotation of said spool inthe seat belt withdrawing direction, wherein said controller sets saidsecond seat belt load limiting mechanism to an inoperative state bysetting said supporting member to the immovable state by actuating saiddriving member when the emergency occurs and said predeterminedcondition is not satisfied, and sets said second seat belt load limitingmechanism to the operative state by setting said supporting member tothe movable state by not actuating said driving member when theemergency occurs and said predetermined condition is satisfied.

Further, a seat belt retractor according to the present invention issuch that said energy absorbing member comprises a long band-like energyabsorbing plate.

Furthermore, a seat belt retractor according to the present invention issuch that said first seat belt load limiting mechanism comprises atorsion bar disposed between said spool and said locking member.

On the other hand, a seat belt apparatus according to the presentinvention comprises at least: a seat belt retractor which winds up aseat belt, a tongue slidably supported on the seat belt withdrawn fromsaid seat belt retractor; and a buckle detachably latched with saidtongue, wherein said seat belt is prevented from being withdrawn by saidseat belt retractor so as to restrain the occupant when the emergencyoccurs, and said seat belt retractor is one of the seat belt retractorsaccording to the present invention.

In addition, a seat belt apparatus according to the present inventionfurther comprises a pretensioner which is actuated to directly rotatesaid spool in the seat belt winding direction when the emergency occurs.

According to the seat belt retractor of the invention having theaforementioned structure and the seat belt apparatus having the same,the limited load on the seat belt in the event of the emergency ischanged by controlling the operation of the first and second seat beltload limiting mechanisms based on information of the situation of theemergency such as preliminary information (the weight of the occupantand the position of a seat in the front-rear direction, and the like),collision-predicting information indicating that a collision is going tooccur, and information indicating the collision severity (the collisionspeed, the acceleration during the collision, and the type of collision,and the like). Therefore, the limited load of the seat belt during acollision can be set more flexibly and variously depending on theconditions under the collision and the information in the emergencysituation, such as the physical size of the occupant. Accordingly, theoccupant can be more effectively and suitably restrained during thecollision.

In this case, the second seat belt load limiting mechanism is actuatedby not actuating the driving member, while the second seat belt loadlimiting mechanism is not actuated by actuating the driving member.Accordingly, when the actuation of the second seat belt load limitingmechanism is required, there is no need to actuate the driving member togenerate reaction gas. Consequently, the occupant is further effectivelyrestrained during the collision because of the effect actuation of thesecond seat belt load limiting mechanism.

When it is determined that the actuation of the second seat belt loadlimiting mechanism is required, but the entire operation of the secondseat belt load limiting mechanism is not required in the event of theemergency, the operation of the second seat belt load limiting mechanismis stopped by actuating the driving member after the second seat beltload limiting mechanism is actuated, but before the entire operation ofthe second seat belt load limiting mechanism is completed. That is, evenafter the second seat belt load limiting mechanism is actuated, it ispossible to stop the operation of the second seat belt load limitingmechanism depending on the emergency situation. Therefore, the kineticenergy absorption (EA) for the occupant in the event of an emergency canbe further finely and correctly conducted.

Further, since the energy absorbing member is provided between thelocking member and the supporting member for the energy absorbingmember, the pretensioner which must operate in the event of theemergency can be arranged to directly rotate the spool in the beltwinding direction.

Further, since the second seat belt load limiting mechanism is disposedcoaxially with the spool, the seat belt retractor is small in thevertical direction. In addition, the first seat belt load limitingmechanism is composed of the torsion bar, thereby achieving the seatbelt retractor having simpler structure and smaller size. The availablespace of the vehicle cabin is thus increased.

Furthermore, since the spool is designed to be rotated in the seat beltwinding direction directly by the pretensioner, the pretensionereffectively conducts the seat belt winding operation in the event of theemergency even though the first and second seat belt load limitingmechanisms are provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration schematically showing a seat belt apparatusprovided with an embodiment of a seat belt retractor according to thepresent invention.

FIG. 2 is a front view of the seat belt retractor of the embodimentshown in FIG. 1.

FIG. 3 is a vertical sectional view showing the seat belt retractor ofthe embodiment shown in FIG. 1.

FIG. 4 is a sectional view schematically showing a second EA mechanismand a driving device of the embodiment shown in FIG. 3.

FIG. 5 is a block diagram for controlling the second EA mechanism andthe driving device of the embodiment shown in FIG. 3.

FIGS. 6( a) through 6(c) are illustrations for explaining the seat beltwinding by a pretensioner when the second EA mechanism is actuated inthe event of the emergency.

FIGS. 7( a) through 7(c) are illustrations for explaining the operationof the second EA mechanism in the event of an emergency.

FIG. 8( a) is a graph showing limited load when the second EA mechanismis actuated, and FIG. 8( b) is a graph showing limited load when thesecond EA mechanism is not actuated.

FIGS. 9( a) through 9(d) are illustrations for explaining the seat beltwinding by the pretensioner when the second EA mechanism is not actuatedin the event of an emergency.

FIGS. 10( a) through 10(d) are illustrations for explaining thenon-operation of the second EA mechanism in the event of an emergency.

FIGS. 11( a) and 11(b) are sectional views partially and schematicallyshowing another embodiment of a seat belt retractor according to thepresent invention.

FIGS. 12( a) and 12(b) show the operable state of the second EAmechanism of the seat belt retractor shown in FIGS. 11( a) and 11(b),wherein FIG. 12( a) is a partial perspective view and FIG. 12( b) is apartial schematic view.

FIGS. 13( a) and 13(b) show the inoperable state of the second EAmechanism of the seat belt retractor shown in FIGS. 11( a) and 11(b),wherein FIG. 13( a) is a partial perspective view and FIG. 13( b) is apartial schematic view.

FIGS. 14( a) and 14(b) are illustrations for explaining the winding andwithdrawal of the seat belt during normal operation of the seat beltretractor of the embodiment shown in FIGS. 11( a) and 11(b).

FIGS. 15( a) through 15(c) are illustrations for explaining theoperation of the second EA mechanism of the seat belt retractor of theembodiment shown in FIGS. 11( a) and 11(b).

FIGS. 16( a) through 16(c) are graphs showing limited load of the seatbelt retractor of the embodiment shown in FIGS. 11( a) and 11(b).

FIGS. 17(1)(a) through 17(1)(d) and FIGS. 17(2)(a) through 17(2)(d) areillustrations for explaining the operation and non-operation of thesecond EA mechanism of the seat belt retractor of the embodiment shownin FIGS. 11( a) and 11(b).

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Hereinafter, preferred embodiments for carrying out the presentinvention will be described with reference to the attached drawings.

FIG. 1 is an illustration schematically showing a seat belt apparatusemploying an embodiment of a seat belt retractor according to thepresent invention.

As shown in FIG. 1, the seat belt apparatus 1 of this embodiment issimilar to a conventionally known seat belt apparatus of a three-pointtype. That is, the seat belt apparatus 1 comprises a seat belt retractor3 which is fixed to a vehicle body near the vehicle seat 2, a seat belt4 which is retracted by the seat belt retractor 3 in such a manner as toallow the withdrawal of the seat belt 4 and is provided at its end witha belt anchor 4 a fixed to a vehicle floor or the vehicle seat 2, adeflection fitting 5 for guiding the seat belt 4 withdrawn from the seatbelt retractor 3 toward an occupant's shoulder, a tongue 6 which isslidably supported on the seat belt 4 guided by and extending from thedeflection fitting 5, and a buckle 7 which is fixed to the vehicle flooror the vehicle seat and to which the tongue 6 can be inserted anddetachably latched.

FIG. 2 is a front view of the seat belt retractor of this embodiment andFIG. 3 is a vertical sectional view of the seat belt retractor of thisembodiment.

As shown in FIGS. 2 and 3, the seat belt retractor 3 of this embodimentcomprises a U-like frame 8 similarly to the emergency locking-type seatbelt retractor (ELR) disclosed in the aforementioned Patent Document 1.A spool 9 onto which the seat belt 4 is wound is rotatably supported bythe frame 8. On one of the side walls (the right-side wall in FIG. 3) 8a of the frame 8, a locking mechanism is disposed. The locking mechanism10 has a locking base (corresponding to the locking member of thepresent invention) 11 rotatably attached to one of the ends of the spool9 and a locking gear 12 rotatably attached to the locking base 11. Onthe other end wall (the left-side wall in FIG. 3) 8 b of the frame 8, apretensioner 13 and a spring mechanism 14 are attached. Between thespool 9 and the locking base 11, a torsion bar (a first EA mechanism;corresponding to the first seat belt load limiting mechanism of thepresent invention) 15 is disposed and, in addition, a second EAmechanism (corresponding to the second seat belt load limiting mechanismof the present invention) 16 is disposed.

The basic operation of the seat belt retractor 3 of this embodiment isthe same as that of the seat belt retractor of the aforementioned PatentDocument 1. That is, in the event of the emergency as mentioned above, adeceleration sensing mechanism (not shown) of a vehicle sensor (notshown) is activated to prevent the locking gear 12 of the lockingmechanism 10 from rotating in the seat belt withdrawing direction. Then,a relative rotation is generated between the locking base 11 and thelocking gear 12 so that a pawl (not shown) attached to the locking base11 pivots and thus engages internal teeth 8 c (shown in FIG. 3) formedin the side wall 8 a of the frame 8. Accordingly, the rotation of thelocking base 11 is stopped so as to prevent the spool 9 from rotating inthe seat belt withdrawing direction. Also when the seat belt is rapidlywithdrawn, the rotation of the locking gear 12 in the seat beltwithdrawing direction is prevented by a webbing sensor (not shown) and,similarly, the rotation of the spool 9 in the seat belt withdrawingdirection is prevented. Specific actions of the seat belt retractor 3will be described later.

FIG. 4 is a sectional view schematically showing the second EA mechanismand the driving device of this embodiment.

As shown in FIGS. 3 and 4, the second EA mechanism 16 of this embodimentcomprises an energy absorbing plate (EA plate) 17 as an energy absorbingmember, an EA plate supporting member 18 which is formed around an outerperiphery of a cylindrical portion 9 a on one end (the right end in FIG.3) of the spool 9 and has an annular disc-like shape, and an EA plateoperating member 19 which is rotatably attached to the EA platesupporting member 18 to operate the energy absorbing plate 17 and has alever-like shape. The seat belt retractor 3 of this embodiment has an EAoperation controlling member 20 for controlling the operation of thesecond EA mechanism 16 by controlling the rotation of the EA platesupporting member 18, and a driving member 21 for driving the EAoperation controlling member 20.

The energy absorbing plate 17 is composed of a long and thin band-likeplate having a predetermined thickness and a predetermined width andhaving elasticity and is formed into an anomalous S-like shape as awhole. The energy absorbing plate 17 may be composed of a bar member.One end portion of the energy absorbing plate 17 is a first supportingportion 17 a fixed to and supported by the locking base 11 and the otherend portion 17 b of the energy absorbing plate 17 can come in contactwith the EA plate operating member 19 in the seat belt winding direction(counter-clockwise direction in FIG. 4). The energy absorbing plate 17has a folded U-like portion 17 c formed in the vicinity of the firstsupporting portion 17 a. A portion between the U-like portion 17 c andthe other end of the energy absorbing plate 17 is normally in contactwith the inner periphery of the cylindrical portion 9 a of the spool 9.

The EA plate supporting member 18 is rotatably and coaxially fitted tothe outer periphery of the cylindrical portion 9 a of the spool 9. Asshown in FIG. 3, normally, the EA plate supporting member 18 isconnected to the spool 9 by a shear pin 22 so that the EA platesupporting member 18 rotates together with the spool 9. Once the shearpin 22 is sheared, the spool 9 and the EA plate supporting member 18 canrotate relative to each other. The EA plate supporting member 18 isprovided with a predetermined number of serration teeth 18 a formed inthe outer periphery thereof.

The EA plate operating member 19 can move between a lying position whereit is retracted in an opening 18 b of the EA plate supporting member 18and a standing position (position shown in FIG. 4) where it extends tothe inner periphery of the cylindrical portion 9 a through an opening 9b of the cylindrical portion 9 a of the spool 9. When the EA plateoperating member 19 is in the standing position as shown in FIG. 4, theEA plate operating member 19 is prevented from pivoting in a direction(counter-clockwise direction in FIG. 4) opposite to a direction towardthe lying position by a circumferential inner end wall 18 c of theopening 18 b. When the EA plate operating member 19 is in the lyingposition of the EA plate supporting member 18, the EA plate operatingmember 19 is not in contact with the both ends of the opening 9 b formedin the cylindrical portion 9 a of the spool 9, wherein the ends extendin a direction perpendicular to the circumferential direction. When theEA plate operating member 19 is in the standing position of the EA platesupporting member 18, the EA plate operating member 19 can be in contactwith the end walls 9 b ₁, 9 b ₂ of the opening 9 b of the spool 9.Therefore, the second EA mechanism 16 is arranged coaxially with thespool 9.

The EA operation controlling member 20 is arranged to face the EA platesupporting member 18. The EA operation controlling member 20 has an arcconcave face as a face thereof facing the EA plate supporting member 18and is provided with a predetermined number of serration teeth 20 awhich are formed in the concave face. The EA operation controllingmember 20 is arranged to move vertically between an inoperative positionas a lower position shown in FIG. 4 where the teeth 20 a do not meshwith the teeth 18 a of the EA plate supporting member 18 and anoperative position as an upper position where the teeth 20 a mesh withthe teeth 18 a of the EA plate supporting member 18. When the EAoperation controlling member 20 is in the inoperative position, theteeth 18, 20 do not mesh with each other so as to allow the rotation ofthe EA plate supporting member 18. When the EA operation controllingmember 20 is in the operative position, the teeth 18, 20 mesh with eachother so as not to allow the rotation of the EA plate supporting member18. Further, the end face opposite to the face facing the EA platesupporting member 18 of the EA operation controlling member 20 is aninclined face 20 b.

As shown in FIG. 3, the driving member 21 is disposed on the side wall 8a of the frame 8. As shown in FIG. 4, the driving member 12 has a gasgenerator 21 a and a driving piston 21 b inside thereof. The gasgenerator 21 a is actuated in the event of an emergency to generatereaction gas and move the driving piston 21 b toward the EA operationcontrolling member 20 by means of the reaction gas. The driving piston21 b has an inclined cam face 21 c on its upper surface and theinclination of the cam face 21 c is set to be the same or substantiallythe same as the inclination of the inclined face 20 b of the EAoperation controlling member 20. When the driving piston 21 b is movedby the reaction gas, the driving piston 21 b enters a space between thebody 21 d of the driving member 21 and the inclined face 20 b of the EAoperation controlling member 20 and moves upward the EA operationcontrolling member 20 because of the cam face 21 c so that the EAoperation controlling member 20 is set to the operative position. Thebody 21 d of the driving member 21 is provided with a guide portion 21 efor guiding the EA operation controlling member 20 during the upwardmovement of the EA operation controlling member 20.

As shown in FIG. 5, the gas generator 21 a of the driving member 21 forcontrolling the operation of the second EA mechanism 16 of thisembodiment is controlled its activation corresponding to an emergencysituation by a CPU (corresponding to the controller of the presentinvention) 29 based on signals outputted from a seat weight sensor 23for detecting the occupant's weight, a seat slide position sensor 24, anacceleration sensor 25 for detecting deceleration of the vehicle, afront satellite sensor 26 for detecting an obstacle in front of thevehicle, a belt withdrawal amount sensor 27, and a buckle switch 28.That is, the second EA mechanism 16 can operate independently from thetorsion bar 15 as the first EA mechanism.

Then, the actions of the seat belt retractor 3 of this embodiment havingthe aforementioned structure will be described. Since actions of theseat belt retractor 3 of this embodiment by the same components as theconventional seat belt retractor 3 disclosed in the aforementionedPatent Document 1 are the same as those of the conventional seat beltretractor 3, the description about those actions will be omitted andonly actions by the characteristic components of the seat belt retractor3 of this embodiment will be described.

As shown in FIG. 4 and FIG. 6( a), when the seat belt 4 is normallyused, the seat belt retractor 3 maintains the energy absorbing plate 17in its inoperative state and maintains the EA plate operating member 19in its standing position. When the standing position of the EA plateoperating member 19 is maintained, the end walls 9 b ₁ of the opening 9b of the spool 9 is in contact with the EA plate operating member 19 andthe free end, i.e. the other end portion 17 b of the energy absorbingplate 17 is in contact with the EA plate operating member 19. Therefore,the standing position of the EA plate operating member 19 is maintained.Therefore, the opening 9 b of the spool 9 is located on the left side ofthe EA plate operating member 19 in FIG. 4 and FIG. 6( a). The spool 9and the EA plate supporting member 18 are connected together by theshear pin 22.

The EA operation controlling member 20 is in the inoperative position sothat the teeth 20 a do not mesh with the teeth 18 a of the EA platesupporting member 18. Further, the gas generator 21 a of the drivingmember 21 is not actuated so that the driving piston 21 b does not enterthe space below the inclined surface 20 b of the EA operationcontrolling member 20.

As a deceleration which is significantly larger than that during thenormal driving acts on the vehicle in the event of the emergency asmentioned above, the pretensioner 13 is actuated. When the CPU 29 judgesthe emergency situation based on the signals outputted from therespective sensors 23, 24, 25, 26, 27 and the buckle switch 28 anddetermines that the absorption of the energy on the occupant by thesecond EA mechanism 16 is also required, that is, that a predeterminedcondition for actuating the second EA mechanism 16 is satisfied such aswhen the occupant has a relatively heavy weight or when a collisionsevere enough to actuate the pretensioner 13 and the airbag occurs, theCPU 29 does not activate the gas generator 21 a of the driving member21.

As shown in FIG. 6( a), the spool 9 is forced to rotate in the seat beltwinding direction α directly by the actuation of the pretensioner 13without the torsion bar 15 intervening. Since the EA operationcontrolling member 20 is set in its inoperative position, the EA platesupporting member 18 is free to rotate. Therefore, as shown in FIGS. 6(a) through 6(c), all of the spool 9, the locking base 11, and the EAplate supporting member 18 start to rotate in the seat belt windingdirection α. Accordingly, a slack of the seat belt 4 worn by theoccupant is removed so as to restrain the occupant. The energy absorbingplate 17 is maintained in its initial state.

As shown in FIG. 6( c), as the winding of the seat belt onto the spool 9by the action of the pretensioner 13 is completed, the seat belt 4starts to be withdrawn by inertia of the occupant. Then, as shown inFIG. 7( a), the spool 9 rotates in the seat belt withdrawing directionβ. Therefore, the EA plate supporting member 18 connected to the spool 9by the shear pin 22 rotates together with the spool 9 in the samedirection β. On the other hand, the pawl pivots to engage the internalteeth 8 c of the frame 8, thereby preventing the locking base 11 fromrotating in the seat belt withdrawing direction β.

Then, since the spool 9 rotates in the seat belt withdrawing direction βand the rotation of the locking base 11 are prevented, the torsion bar15 is torsionally deformed similarly to the conventional one. That is,the torsion bar 15 conducts the EA action so that the inertia energy ofthe occupant is absorbed by the torsion bar 15. At the same time, asshown in FIG. 7( b), the spool 9 and the EA plate supporting member 18rotate together in the seat belt withdrawing direction β so that the oneend wall 9 b ₁ of the opening 9 b of the spool 9 presses the EA plateoperating member 19 in the seat belt withdrawing direction β.

Then, as shown in FIG. 7( b), the energy absorbing plate 17 is deformedsuch that the U-like portion 17 c gradually moves toward the other endportion 17 b side. Accordingly, the energy applied to the occupant isalso absorbed by the second EA mechanism 16. Therefore, as shown in FIG.8( a), the limited load (EA load) becomes the sum of the load bytorsional deformation of the torsion bar 15 and the load by deformationof the energy absorbing plate 17. Because of both of the deformation ofthe torsion bar 15 and the deformation of the energy absorbing plate 17of the second EA mechanism 16, the energy applied to the occupant iseffectively absorbed. As the deformation of the energy absorbing plate17 is finished, the EA load becomes the load solely by the torsionaldeformation of the torsion bar 15.

As the energy absorbing plate 17 is completely reversed so that theenergy absorption by the energy absorbing plate 17 is finished as shownin FIG. 7( c), the energy applied to the occupant is effectivelyabsorbed solely by the torsion bar 17 as shown in FIG. 8( a).

As mentioned above, the second EA mechanism 16 effectively operateswithout actuating the gas generator 21 a of the driving member 21, i.e.without generating reaction gas.

On the other hand, when the CPU 29 judges the emergency situation basedon the signals outputted from the respective sensors 23, 24, 25, 26, 27and the buckle switch 28 and determines that the absorption of theenergy by the second EA mechanism 16 is not required, that is, that theaforementioned predetermined condition for actuating the second EAmechanism 16 is not satisfied such as when the occupant has a relativelylight weight or when such a mild collision that the pretensioner 13 orthe airbag is not actuated occurs, the CPU 29 actuates the gas generator21 a of the driving member 21. Therefore, the gas generator 21 agenerates reaction gas to move the driving piston 21 b so that thedriving piston 21 b enters the space below the EA operation controllingmember 20 as shown in FIG. 9( b). Then, by the inclined face 21 c of theEA operation controlling member 20 and the cam face 21 c of the drivingpiston 21 b, the EA operation controlling member 20 is moved upward tothe operative position where the teeth 20 a mesh with the teeth 18 a ofthe EA plate supporting member 18. Therefore, the EA plate supportingmember 18 is prevented from rotating.

Similarly to the aforementioned case, as shown in FIG. 9( a), the spool9 starts to be rotated in the seat belt winding direction α because ofthe actuation of the pretensioner 13. Since the EA plate supportingmember 18 is prevented from rotating, the spool 9, the locking base 11,and the energy absorbing plate 17 are about to rotate in the seat beltwinding direction α. Therefore, as shown in FIG. 9( b), the shear pin 22is sheared so that the spool 9, the locking base 11, and the energyabsorbing plate 17 rotate in the seat belt winding direction α relativeto the EA plate supporting member 18. Then, the end of the other endportion 17 b of the energy absorbing plate 17 moves the EA plateoperating member 19 to pivot toward the lying position and, after that,the other end wall 9 b ₂ of the opening 9 b of the spool 9 further movesthe EA plate operating member 19 to pivot toward the lying position. Inthis manner, the spool 9 rotates together with the locking base 11 andthe energy absorbing plate 17 in the seat belt winding direction α withmoving the EA plate operating member 19 to pivot. As shown in FIG. 9(c), the EA plate operating member 19 is set to the lying position.

As shown in FIG. 9( d), as the seat belt winding onto the spool 9 by theaction of the pretensioner 13 is terminated, the seat belt 4 starts tobe withdrawn by inertia of the occupant similarly to the aforementionedcase so that, as shown in FIG. 10( a), the spool 9 rotates in the seatbelt withdrawing direction β. However, since the locking base 11 isprevented from rotating in the belt withdrawing direction β similarly tothe aforementioned case and the EA plate operating member 19 is set tothe lying position, the locking base 11 does not rotate and energyabsorbing plate 17 keeps its initial state and is not deformed even whenthe spool 9 rotates. Therefore, as shown in FIGS. 10( b) through 10(d),only the spool 9 rotates in the seat belt withdrawing direction β.Therefore, as shown in FIG. 8( b), the EA load becomes the load solelyby the torsional deformation of the torsion bar 15. Therefore, theenergy absorption by the deformation of the energy absorbing plate 17 isnot conducted and the energy applied to the occupant is absorbed solelyby the torsion bar 15.

In this manner, the limited load of the seat belt 4 is set to be smallwhen, based on the signals outputted from the respective sensors 23, 24,25, 26, and 27, the CPU determines that the energy absorption by thesecond EA mechanism 16 is not required such as when such a mildcollision that the pretensioner 13 and the airbag is not actuated (forexample, a mild collision of a vehicle running at a speed of 30 km/houror less) occurs.

That is, the load limitation by the second EA mechanism 16 is selectedsuch that there is a case that the load limitation is conducted in theevent of an emergency and a case that the load limitation is notconducted in the event of an emergency.

According to the seat belt retractor 3 of this embodiment, the limitedload of the seat belt in the event of an emergency is changed based oninformation of the situation of the emergency such as preliminaryinformation (the weight of an occupant and the position of a seat in thefront-rear direction, and the like), collision-predicting informationindicating that a collision is predicted, and information indicating thecollision severity (the collision speed, the acceleration during thecollision, and the type of collision, and the like). Therefore, thelimited load of the seat belt during a collision can be set moreflexibly and variously in accordance with the information of theemergency situation, such as the conditions of the collision and thephysical size of the occupant. Accordingly, the occupant can be moreeffectively and suitably restrained during a collision.

In this case, the second EA mechanism is actuated by not actuating thedriving member 21, while the second EA mechanism 16 is not actuated byactuating the driving member 21. Accordingly, when the actuation of thesecond EA mechanism 16 is required, there is no need to actuate thedriving member to generate reaction gas. Consequently, the occupant isfurther effectively restrained during a collision because of the effectactuation of the second EA mechanism 16.

Since the energy absorbing plate 17 is provided between the locking base11 and the EA plate supporting member 18, the pretensioner 13 which mustoperate in the event of an emergency can be disposed to directly rotatethe spool 9 in the belt winding direction α.

Further, since the second EA mechanism 16 is disposed integrally andcoaxially with the spool 9, the seat belt retractor 3 which issmall-sized in the vertical direction is achieved, thereby increasingthe effective space of the vehicle cabin.

Furthermore, since the spool 9 is designed to be rotated in the seatbelt winding direction α directly by the pretensioner 13 without thetorsion bar 15 intervening, the pretensioner 13 effectively exhibits theseat belt winding in the event of an emergency even though the torsionbar 15 and the second EA mechanism 16 are provided.

The other structure and the other works and effects of the seat beltretractor 3 are the same as those of the seat belt retractor 3 disclosedin Patent Document 1, which is incorporated herein by reference.

FIGS. 11( a), 11(b) through FIG. 13( a), 13(b) are illustrationspartially and schematically showing another embodiment of the seat beltretractor according to the present invention.

In the aforementioned embodiment, in case of not actuating the second EAmechanism 16 in the event of an emergency, the EA plate operating member19 is moved to the lying position by the seat belt winding action of thepretensioner 13 when the gas generator 21 a of the driving member 21 isactuated, thereby setting the second EA mechanism 16 to the inoperativestate. For this, if the second EA mechanism 16 is first actuated in theevent of an emergency, it is impossible to stop the operation of thesecond EA mechanism 16 on the way even when the gas generator 21 a isactuated in order to stop the operation of the second EA mechanism 16.In the aforementioned embodiment, that is, once the second EA mechanism16 is actuated, it is impossible to stop the operation of the second EAmechanism 16 until the operation of the second EA mechanism 16 iscompletely terminated whether or not the generator 21 a is actuated ornot.

On the other hand, in the seat belt retractor 3 of this embodiment, itis possible to stop the operation of the second EA mechanism 16 on theway. In other words, in the seat belt retractor 3 of this embodiment,the operation of the second EA mechanism 16 is controllable selectivelyto be stopped or not stopped. Hereinafter, the seat belt retractor 3 ofthis embodiment will be described.

As shown in FIGS. 11( a) and 11(b), the seat belt retractor 3 of thisembodiment comprises a casing 30 (corresponding to the supporting memberfor the energy absorbing member of the present invention) which isdisposed in the cylindrical portion 9 a on one end side (the right sidein FIG. 11( a)) of the spool 9. The casing 30 is formed in a bottomedcylindrical member having a cylindrical portion 30 a and a bottom 30 b.In this case, the cylindrical portion 30 a of the casing 30 is disposedinside the cylindrical portion 9 a of the spool 9 and the shaft portionof the locking base 11 penetrates through a circular hole, which isformed in the bottom of the casing 30, without touching the casing 30.

On the inner periphery of the cylindrical portion 30 a of the casing 30,an EA plate operating portion 31 which is a convex portion projectingradially is provided. The EA plate operating portion 31 actuates thesecond EA mechanism 16 similarly to the EA plate operating member 19 ofthe aforementioned embodiment.

Between the spool 9 and the casing 30, a rod-like stopper 32 is fittedin grooves formed in the spool 9 and the casing 30 such that the stopper32 is slidable. Therefore, when the stopper 32 is positioned between thespool 9 and the casing 30, the spool 9 and the casing 30 are not allowedto rotate relative to each other so that they rotate together. When thestopper 32 is not positioned between the spool 9 and the casing 30, thespool 9 and the casing 30 are allowed to rotate relative to each other.The stopper 32 has a pair of shear pins 32 a projecting therefrom. Asthe shear pins 32 a are fitted into the grooves of the spool 9, thestopper 32 is normally held between the spool 9 and the casing 30 asshown in FIG. 11( b).

As shown in FIG. 11( a) and FIG. 12( a), a stopper operating member 33and an EA operation controlling member 32 are disposed on the outerperiphery of the cylindrical portion 9 a of the spool 9. The stopperoperating member 33 is formed in an annular shape and is not allowed torotate relative to the frame 8 and is allowed to move in the axialdirection of the spool 9. As the stopper operating member 33 moves inthe axial direction of the spool 9, the stopper 32 is pressed by thestopper operating member 33 so as to get out of the groove of the casing30. As the stopper 32 gets out of the groove of the casing 30, the spool9 and the casing 30 are allowed to rotate relative to each other.

The EA operation controlling member 34 has an annular portion 34 a ofwhich diameter is the same as that of the stopper operating member 33,and a long operating lever 34 b extending radially outwardly from theannular portion 34 a. The stopper operating member 33 and the annularportion 34 a of the EA operation controlling member 34 are opposed toeach other in the axial direction of the spool 9. On the opposed facesof the stopper operating member 33 and the EA operation controllingmember 34, a movement converting mechanism 35 for converting therotation of the EA operation controlling member 34 to the axial movement(i.e. linear movement) of the stopper operating member 33 is provided.As shown in FIG. 12( a) and FIG. 13( a), the movement convertingmechanism 35 comprises a stopper operating member side corrugatedportion 33 a and an EA operation controlling member side corrugatedportion 34 c which are annular and formed in the opposed faces of thestopper operation member 33 and the EA operation controlling member 34,respectively.

Normally, as shown in FIG. 12( a), the stopper operating member 33 andthe EA operation controlling member 34 are set to the inoperativeposition where the peaks of the stopper operating member side corrugatedportion 33 a and the valleys of the EA operation controlling member sidecorrugated portion 34 c are opposed to each other and the valleys of thestopper operating member side corrugated portion 33 a and the peaks ofthe EA operation controlling member side corrugated portion 34 c areopposed to each other. In the inoperative position of the stopperoperating member 33 and the EA operation controlling member 34, therespective corrugated surfaces of the stopper operating member 33 andthe EA operation controlling member 34 are wholly or substantiallywholly in contact with each other. In this state, the stopper operatingmember 33 is placed at a position closest to the EA operationcontrolling member 34 in the axial direction of the spool 9.

When the EA operation controlling member 34 rotates relative to thestopper operating member 33 in the event of an emergency, as shown inFIG. 13( a), the stopper operating member 33 and the EA operationcontrolling member 34 are set to the operative position where the peaksof the stopper operating member side corrugated portion 33 a and thepeaks of the EA operation controlling member side corrugated portion 34c are opposed to each other and the valleys of the stopper operatingmember side corrugated portion 33 a and the valleys of the EA operationcontrolling member side corrugated portion 34 c are opposed to eachother. In the operative position of the stopper operating member 33 andthe EA operation controlling member 34, only the peaks of the respectivecorrugated surfaces of the stopper operating member 33 and the EAoperation controlling member 34 are in contact with each other. In thiscase, the stopper operating member 33 moves in the axial direction ofthe spool 9 and is thus place at a position farthest from the EAoperation controlling member 34 in the axial direction of the spool 9.In the operative position of the stopper operating member 33 and the EAoperation controlling member 34, the stopper 32 is pressed by thestopper operating member 33 to get out of the groove of the casing 30.

As shown in FIGS. 11( a), 11(b) and FIG. 12( b), an operation lever 34 bof the EA operation controlling member 34 has a tip end 34 b ₁ which isformed by folding at a right angle or a substantially right angle. Thetip end 34 b ₁ penetrates a circular guide hole 36, which is formed inone side wall 8 a of the frame 8 coaxially with the spool 9. The tip end34 b ₁ of the operation lever 34 b penetrating the guide hole 36 furtherenters into a guide hole 21 f of the driving piston 21 b of the drivingmember 21.

The tip end 34 b ₁ of the operation lever 34 b is normally located atone end 36 a of the guide hole 36 as shown in FIG. 11( b). When the tipend 34 b ₁ is located at this position, as shown in FIGS. 12( a) and12(b), the stopper operating member 33 and the EA operation controllingmember 34 are located at the inoperative position and the driving piston21 b in the inoperative state is in contact with the tip end 34 b ₁. Onthe other hand, when the gas generator 21 a of the driving member 21 isactuated, the driving piston 21 b is actuated by gas generated from thegas generator 21 a to press the tip end 34 b ₁ of the operation lever 34b. Accordingly, the tip end 34 b ₁ is moved to rotate the EA operationcontrolling member 34 so that the stopper operating member 33 is movedin the axial direction of the spool 9 by means of the movementconverting mechanism 35. As the tip end 34 b ₁ arrives at the other end36 b of the guide hole 36, the top end 34 b ₁ is stopped at thisposition. When the tip end 34 b ₁ is located at this position, as shownin FIGS. 13( a) and 13(b), the stopper operating member 33 and the EAoperation controlling member 34 are located at the operative position.

The other components of the seat belt retractor 3 of this embodiment arethe same as those of the aforementioned embodiment.

In the seat belt retractor 3 of this embodiment structured as mentionedabove, normally the stopper operating member 33 and the EA operationcontrolling member 34 are set at the inoperative position. In thisstate, the stopper 32 is located between the spool 9 and the casing 30.In addition, the locking base 11 is allowed to rotate together with thespool 9. Therefore, the spool 9, the locking base 11, and the casing 30are allowed to rotate together. That is, as the seat belt 4 is withdrawnat a normal withdrawing speed for wearing the seat belt 4, the spool 9,the locking base 11, and the casing 30 rotate together in the seat beltwithdrawing direction from a position shown in FIG. 14( a) to a positionshown in FIG. 14( b) so that the seat belt 4 is withdrawn. On the otherhand, when the seat belt wearing is cancelled, the spool 9, the lockingbase 11, and the casing 30 rotate together in the seat belt windingdirection as the opposite direction so that the seat belt 4 is wound uponto the spool 9 by the spring mechanism 14. During this, even thoughthe spool 9, the locking base 11, and the casing 30 rotate together, thestopper operating member 33 and the EA operation controlling member 34are maintained at the inoperative position.

In the event of an emergency as mentioned above, the pretensioner 13 isactuated similarly to the aforementioned case. Further, similarly to theaforementioned embodiment, it is assumed that the CPU 29 determines thatthe operation of the second EA mechanism 16 is required. In this case,the CPU 29 does not actuate the gas generator 21 a so that the stopperoperating member 33 and the EA operation controlling member 34 aremaintained at the inoperative position. As the pretensioner 13 isactuated in this state, the spool 9, the locking base 11, and the casing30 are rotate together in the seat belt winding direction, therebyremoving a slack of the seat belt 4. Then, the seat belt 4 is withdrawnbecause of inertia of the occupant. At this point, since the lockingbase 11 is prevented from rotating in the belt withdrawing direction bythe locking mechanism 10, only the spool 9 and the casing 30 rotatetogether in the seat belt withdrawing direction.

Then, the torsion bar 15 is torsionally deformed similarly to theaforementioned embodiment. Since the energy absorbing plate 17 ispressed by the EA plate operating portion 31 of the casing 30, theenergy absorbing plate 17 is gradually deformed as shown in FIGS. 15( a)through 15(c), similarly to the aforementioned embodiment. That is, theEA action by the first EA mechanism (the torsion bar 15) and the EAaction by the second EA mechanism 16 are both conducted. Therefore, asshown in FIG. 16( a), the EA load becomes the sum of the load bytorsional deformation of the torsion bar 15 and the load by deformationof the energy absorbing plate 17 (similarly to the case shown in FIG. 8(a) of the embodiment). Because of both of the deformation of the torsionbar 15 and the deformation of the energy absorbing plate 17 of thesecond EA mechanism 16, the energy applied to the occupant iseffectively absorbed. As the deformation of the energy absorbing plate17 is finished, the EA load becomes the load solely by the torsionaldeformation of the torsion bar 15.

It is assumed that, in the event of an emergency during normal operationof the seat belt retractor 3 as shown in FIGS. 17(1)(a) and 17(2)(a),the CPU 29 determines that the operation of the second EA mechanism 16is not required similarly to the aforementioned embodiment. At thispoint, as shown in FIGS. 17(1)(c) and 17(2)(c), the CPU 29 actuates thegas generator 21 a so that the gas generator 21 a generates gas. Withthe gas generated, the driving piston 21 b presses the tip end 34 b ₁ ofthe operation lever 34 b so that the tip end 34 b ₁ moves to the left inFIG. 12( b) and the annular portion 34 a of the EA operation controllingmember 34 rotates in the clockwise direction in FIG. 12( b) by theoperation lever 34 b. Then, as shown in FIGS. 17(1)(d) and 17(2)(d), thetip end 34 b ₁ comes at the other end 36 b of the guide hole 36, therebystopping the rotation of the annular portion 34 a.

As the annular portion 34 a rotates, the stopper operating member 33 isforced by the movement converting mechanism 35 in a direction γ so as topress the stopper 32, thereby shearing the shear pins 32 a. Accordingly,the stopper operating member 33 moves in the direction γ and the stopper32 also moves in the direction γ to get out of the groove of the casing30. As a result of this, the spool 9 and the casing 30 are allowed torotate relative to each other. Therefore, the spool 9 rotated in theseat belt withdrawing direction β because the seat belt 4 is forced tobe withdrawn due to the inertia of the occupant.

Since the casing 30 does not rotate even though the spool 9 rotates, theenergy absorbing plate 17 keeps its initial state and is not deformed.Therefore, only the spool 9 rotates in the seat belt withdrawingdirection β similarly to the aforementioned embodiment. Accordingly, theEA load becomes the load solely by the torsional deformation of thetorsion bar 15 as shown in FIG. 16( b). In this manner, the energyabsorption by deformation of the energy absorbing plate 17 is notconducted so that the energy applied to the occupant is absorbed solelyby the torsional deformation of the torsion bar 15.

Further, it is assumed that, in the event of an emergency during normaloperation of the seat belt retractor 3 as shown in FIGS. 17(1)(a) and17(2)(a), the CPU 29 determines that the operation of the second EAmechanism 16 is required similarly to the aforementioned embodiment, butthe entire operation of the second EA mechanism is not required. In thiscase, as shown in FIGS. 17(1)(b) and 17(2)(b), the EA action by thefirst EA mechanism (the torsion bar 15) and the EA action by the secondEA mechanism 16 are both conducted. Therefore, as shown in FIG. 16( c),the EA load becomes the sum of the load by torsional deformation of thetorsion bar 15 and the load by deformation of the energy absorbing plate17. However, if the CPU 29 determines that the operation of the secondEA mechanism 16 is not required on the way of deformation of the energyabsorbing plate 17, the CPU 29 actuates the gas generator 21 a as shownin FIGS. 17(1)(c) and 17(2)(c). Then, the operation of the second EAmechanism 16 is stopped so that the energy absorbing plate 17 no moredeforms before the entire deformation of the energy absorbing plate 17is completed. Accordingly, the EA load becomes the load solely by thetorsional deformation of the torsion bar 15 because of no load by thedeformation of the energy absorbing plate 17 shown by a two-dot chainline in FIG. 16( c) before the entire deformation of the energyabsorbing plate 17 is completed.

The timing of stopping the deformation of the energy absorbing plate 17on the way of deformation of the energy absorbing plate 17 is determinedand set by the CPU 29 according to the emergency situation. In theaforementioned embodiment, the CPU 29 determines whether or not theoperation of the second EA mechanism 16 is required to be stopped duringthe operation of the second EA mechanism. However, immediately after theemergency, the CPU 29 may determine whether or not the operation of thesecond EA mechanism 16 is required to be stopped after actuation of thesecond EA mechanism 16.

According to the seat belt retractor 3 of this embodiment, when the CPU29 determines that the operation of the second EA mechanism 16 isrequired, but the entire operation of the second EA mechanism 16 is notrequired, the gas generator 21 a is actuated after the second EAmechanism 16 is actuated but before the entire operation of the secondEA mechanism 16 is completed. That is, even after the second EAmechanism 16 is actuated, it is possible to stop the operation of thesecond EA mechanism 16 depending on the emergency situation. Therefore,the kinetic energy absorption (EA) for the occupant in the event of anemergency can be further finely and correctly conducted. The other worksand effects of the seat belt retractor 3 of this embodiment are the sameas those of the aforementioned embodiment.

Though the pretensioner 13 is actuated after the gas generator 21 a ofthe driving member 21 is actuated in case of not actuating the second EAmechanism 16 in the aforementioned embodiments, the present invention isnot limited thereto. That is, in case of not actuating the second EAmechanism 16, the driving member 21 and the pretensioner 13 may beactuated at the same time.

Though the gas generator 21 a is used as the driving member 21 in theaforementioned embodiments, the present invention is not limitedthereto. That is, the driving piston 21 b may be actuated by drivingforce of another means using electromagnetic force such as anelectromagnetic solenoid. In this case, the electromagnetic solenoid iscontrolled by the CPU 29 similarly to the aforementioned case. Briefly,various design changes may be made within a scope of the claims of thepresent invention.

The seat belt retractor of the present invention is suitably used as aseat belt retractor which is used in a seat belt apparatus installed ina vehicle such as an automobile and which prevents a seat belt frombeing withdrawn with absorbing energy on the occupant by limiting loadapplied on a seat belt in the event of an emergency.

The disclosures of Japanese Patent Applications No. 2008-293396 filed onNov. 17, 2008, and No. 2009-027179 filed on Feb. 9, 2009, areincorporated by references.

While the invention has been explained with reference to the specificembodiments of the invention, the explanation is illustrative and theinvention is limited only by the appended claims.

1. A method of limiting a load applied on a seat belt in an emergency,comprising: obtaining information comprising collision-predictinginformation and collision severity information based on an emergencysituation; judging if the emergency situation is in a first situationwherein a predetermined condition for controlling one seat belt loadlimiting mechanism is not satisfied based on the information, or in asecond situation wherein the predetermined condition for controlling theone seat belt load limiting mechanism is satisfied based on theinformation; in the first situation, actuating a driving member not tooperate the one seat belt load limiting mechanism; winding the seat beltto remove a slack of the seat belt with actuating the driving member;and operating another seat belt load limiting mechanism to preventwithdrawing the seat belt; or in the second situation, winding the seatbelt to remove the slack of the seat belt without actuating the drivingmember; and operating the one and another seat belt load limitingmechanisms to prevent withdrawing the seat belt.
 2. A method of limitinga load applied on a seat belt in an emergency according to claim 1,wherein the second situation further comprises judging if the emergencysituation is in a further situation wherein an entire operation of theone seat belt load limiting mechanism is not required, while operatingthe one and another seat belt load limiting mechanisms; in the furthersituation, actuating the driving member not to operate the one seat beltload limiting mechanism; and continuously operating the another seatbelt load limiting mechanism to prevent withdrawing the seat belt.
 3. Amethod of limiting a load applied on a seat belt in an emergencyaccording to claim 2, wherein a torsion bar is deformed to absorb aninertia energy of the occupant when operating the another seat belt loadlimiting mechanism, and an energy absorbing member is deformed to absorbthe inertia energy of the occupant when operating the one seat belt loadlimiting mechanism.
 4. A method of limiting a load applied on a seatbelt in an emergency according to claim 3, wherein the collisionseverity information includes a collision speed, and an acceleration anddeceleration during a collision.
 5. A method of limiting a load appliedon a seat belt in an emergency according to claim 4, wherein theinformation further comprises preliminary information including a weightof an occupant, and a position of a seat in a front-rear direction.
 6. Amethod of limiting a load applied on a seat belt in an emergencyaccording to claim 5, wherein a reaction gas is generated when actuatingthe driving member not to operate the one seat belt load limitingmechanism.
 7. A method of limiting a load applied on a seat belt in anemergency according to claim 6, wherein a pretensioner is actuated whenwinding the seat belt to remove the slack of the seat belt.